SEO (search engine optimization) is the work of improving a website so it is found more often in the unpaid, organic results of search engines. It covers making pages accessible and understandable to search engines and making their content match what people search for.
At a glance
- Type
- Discipline, umbrella term for work on a website
- Affects
- unpaid (organic) search results
- Stages at Google
- Crawling, indexing, serving search results
- Measured by
- Clicks, impressions, CTR, average position (Search Console)
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How does SEO work?
Google describes its search in three stages. During crawling, a program called Googlebot downloads pages it discovers through links, known URLs or submitted sitemaps. During indexing, Google analyzes text, images and video and stores the information in a large database. During serving, Google returns the results it considers most relevant for a query.
SEO works on all three stages. A page that cannot be crawled will not be indexed, and an indexed page only ranks if it fits the query. Google’s own SEO Starter Guide sums up the job as helping search engines understand content and helping users find a site and decide whether to visit it.
Google states that it does not accept payment to rank pages higher. Ads in search results are a separate discipline called paid search. SEM (search engine marketing) is the umbrella term for SEO and paid search, although many people use it for paid search only.
Areas of SEO
In practice, SEO is commonly split into three areas:
- Technical SEO: accessibility, crawling, indexing, redirects, page speed, mobile rendering, structured data.
- On-page and content: content that answers a search intent, plus title tags, headings and internal links.
- Off-page: signals from outside the site, mainly links from other websites.
This split is an industry convention. Google organizes its own documentation differently, by crawling and indexing, appearance in search, and spam policies. Local SEO, image SEO and international SEO are often added as specialties.
SEO and AI search
With AI-generated answers in search engines, part of the discussion has moved to GEO (generative engine optimization). For Google Search, Google says there are no additional requirements to appear in AI Overviews or AI Mode. A page has to be indexed and eligible to be shown with a snippet. Basic SEO therefore remains a requirement for visibility in Google’s AI features.
| Term | Full form | Goal | Metric | Origin of the term |
|---|---|---|---|---|
| SEO (this term) | Search engine optimization | Help search engines understand content and help users find a site through search | Clicks, impressions, CTR and average position in the Search Console performance report | no clear first source; Google uses the term in its own documentation |
| GEO | Generative engine optimization | Increase the visibility of content in responses from generative search systems | in the research paper “Position-Adjusted Word Count” and “Subjective Impression”; for Google Search, impressions in the generative AI features performance report (since 2026-08-31) | Aggarwal et al., “GEO: Generative Engine Optimization”, arXiv:2311.09735 (2023-11-16), KDD 2024 |
| AEO | Answer engine optimization | Appear as a direct answer or source in answer systems (industry usage, no standard) | no defined metric | no clear first source |
| AI SEO | – | Umbrella term for SEO in AI-powered search, sometimes also for using AI tools in SEO work (industry usage) | no defined metric | no clear first source |
| LLMO / LLM SEO | Large language model optimization | Be mentioned in answers from large language models (industry usage, often used interchangeably with GEO) | no defined metric | no clear first source |
The table describes terms and does not rate methods. For AI Overviews and AI Mode, Google names no requirements beyond the basics of Search. The terms GEO, AEO and LLMO do not appear in Google's documentation on AI features. Goals without a primary source reflect industry usage. Sources: Aggarwal, P. et al.: GEO: Generative Engine Optimization. arXiv:2311.09735 (2023), KDD 2024; Google Search Central: SEO-Startleitfaden / SEO Starter Guide; Search-Console-Hilfe: Leistungsbericht (Suche) / Performance report (Search); Search-Console-Hilfe: Leistungsbericht zu generativen KI-Funktionen (Google Suche); Google Search Central: KI-Funktionen und deine Website / AI features and your website. Last checked: .
Example
An online store notices that its category pages get little search traffic. An analysis finds three causes. Filter URLs create thousands of near-identical pages, category pages share identical title tags, and no category explains what it contains. The fixes span all three areas: keep filter URLs from being crawled (technical), write distinct titles and descriptions (on-page), and ask manufacturers to link to the store (off-page).
FAQ
Can you do SEO yourself? Yes. Google’s SEO Starter Guide is written for site owners without an SEO background. Larger sites with many templates, languages or filter combinations usually need more technical expertise.
How long does SEO take to work? Google gives no fixed time frame. Some changes may take effect within a few hours, others after several months, according to Google.
Can anyone guarantee a number one ranking? No. Google’s SEO Starter Guide says there are no secrets that will automatically rank a site first.
Sources
- SEO Starter Guide – Google Search Central (last updated 2025-12-10)developers.google.com
- In-depth guide to how Google Search works – Google Search Centraldevelopers.google.com
- AI features and your website – Google Search Central (last updated 2025-12-10)developers.google.com
- Search engine optimization – Wikipedia (secondary source, term history)en.wikipedia.org
- Aggarwal et al.: GEO: Generative Engine Optimization (arXiv:2311.09735)arxiv.org
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